Device with a hollow output beam

Abstract

A laser (14) includes an optical amplifier array system (17) that generates a plurality of laser beams (24); and a beam combiner (18) that coherently combines the plurality of laser beams (24) to form a combination beam (26) having a hollow center in a near field. The combination beam (26) with the hollow center allows for the use of a beam director (19) having an on-axis, reflective beam expander (21) without (i) loss in power, (ii) degradation of beam quality, or (iii) excessive heating of the beam expander (21).

What is claimed is: 
     
         1 . A laser comprising:
 an optical amplifier array system that generates a plurality of laser beams; and   a beam combiner that coherently combines the plurality of laser beams to form a combination beam having a hollow center in a near field.   
     
     
         2 . The laser of  claim 1  wherein the optical amplifier array system generates at least six laser beams which have the same wavelength and approximately the same phase. 
     
     
         3 . The laser of  claim 2  wherein at least six of laser beams in the combination beam propagate along parallel axes and are positioned side-by-side. 
     
     
         4 . The laser of  claim 1  further comprising an on-axis beam expander that adjusts the combination beam to provide an assembly beam that has a hollow center in the near field and characteristics of a solid beam in a far field. 
     
     
         5 . The laser of  claim 4  wherein the on-axis beam expander includes a plurality of reflective elements that expand the combination beam. 
     
     
         6 . The laser of  claim 1  wherein the combination beam has a power of at least six kilowatts. 
     
     
         7 . The laser of  claim 1  wherein the optical amplifier array system includes a seed laser that generates a seed output beam, a fiber splitter that splits the seed output beam into a plurality of seed split beams, and an amplifier assembly that amplifies each of the seed split beams to generate the plurality of laser beams. 
     
     
         8 . The laser of  claim 1  wherein the beam combiner directs the plurality of laser beams to be substantially parallel to and spaced apart from a combination axis of the combination beam. 
     
     
         9 . The laser of  claim 1  wherein the beam combiner includes a plurality of combiner fibers for transmitting and launching the plurality of laser beams, wherein each combiner fiber has a fiber outlet, and wherein the fiber outlets are spaced apart and arranged in an outlet pattern having a hollow center. 
     
     
         10 . The laser of  claim 1  wherein the beam combiner coherently combines the plurality of laser beams so that the combination beam has a substantially annular shaped cross-section with a substantially circular outer diameter and a substantially circular inner diameter. 
     
     
         11 . The system that comprises the laser of  claim 1 , a beam pointer that selectively steers the combination beam, and on-axis beam expander that expands the combination beam to provide an assembly beam that has a hollow center in the near field and characteristics of a solid beam in a far field. 
     
     
         12 . A method for generating a combination beam, the method comprising:
 generating a plurality of laser beams; and   coherently combining the plurality of laser beams to form a combination beam having a hollow center in a near field region.   
     
     
         13 . The method of  claim 12  wherein generating includes generating at least six laser beams which have the same wavelength and approximately the same phase. 
     
     
         14 . The method of  claim 13  wherein generating includes the six of laser beams in the combination beam propagate along parallel axes and are positioned side-by-side. 
     
     
         15 . The method of  claim 12  further comprising adjusting the combination beam with an on-axis beam expander to provide an assembly beam that has a hollow center in the near field and characteristics of a solid beam in a far field. 
     
     
         16 . The method of  claim 15  wherein adjusting includes the on-axis beam expander having a diverging element and a collimating element. 
     
     
         17 . The method of  claim 16  further comprising coupling the diverging element to the collimating element with a structural frame, wherein coherently combining includes combining the plurality of laser beams so that the combination beam has a substantially annular shaped cross-section with a substantially circular outer diameter and a substantially circular inner diameter; and wherein the combination beam has a gap to allow the combination beam to not be obstructed by the structural frame. 
     
     
         18 . The method of  claim 12  wherein generating includes generating a seed output beam with a seed laser, splitting the seed output beam into a plurality of seed split beams with a fiber splitter, and amplifying each of the seed split beams with an amplifier assembly to generate the plurality of laser beams. 
     
     
         19 . The method of  claim 12  wherein coherently combining includes using a beam combiner to direct the plurality of laser beams to be substantially parallel to and spaced apart from a combination axis of the combination beam. 
     
     
         20 . The method of  claim 12  wherein coherently combining includes using a beam combiner that includes a plurality of combiner fibers for transmitting and launching the plurality of laser beams, wherein each combiner fiber has a fiber outlet, and wherein the fiber outlets are spaced apart and arranged in an outlet pattern having a hollow center. 
     
     
         21 . The method of  claim 12  wherein coherently combining includes using a beam combiner that coherently combines the plurality of laser beams so that the combination beam has a substantially annular shaped cross-section with a substantially circular outer diameter and a substantially circular inner diameter.